Induction unit control system

ABSTRACT

The individual induction units employed in a multi-room air conditioning system are each provided with a damper for varying the flow of the primary air into the induction unit. This damper is automatically controlled in response to the pressure differential across the nozzle plate, that is between the pressure existing inside the primary air supply plenum, and the ambient pressure.

United States Patent Newton 1 1 Mar. 21, 1972 541 INDUCTION UNIT CONTROLSYSTEM 1,936,544 11/1933 Shurtleff ..236/38 1721 AlwinB-Newtoflmklaiiii51322 QZ'LZfZi'J; .::::..?2fi2 [73] Assignee: Borg-Warner Corporation,Chicago, Ill.

Primary Examiner-Carroll B. Dority, Jr. [22] Filed: Apr. 30, 1970AttorneyDonald W. Banner, William S. McCurry and John [21] Appl. No.:33,448 Butcher [57] ABSTRACT 52 l .165 40, 165 16,165123, I 1 U s C l23/6/38 The individual mduction units employed 1n a multl-room air IB60}. 1 conditioning system are each provided with a damper for vary-[5l] lnt.C th fl fth th d V TH 58] FieldofSenrch..l65/16,40,l23;236/38,92 e *F m P e m damper 1s automaticallycontrolled in response to the pressure [56] References and differentialacross the nozzle plate, that is between the pressure existing insidethe primary air supply plenum, and the am- UNITED STATES PATENTS biemPressure 3,223,149- 12/1965 Miner ..l65/l23 X 10 Claims, 3 DrawingFigures I 2 4 PM, ILL w 1 v11 4! v if i 55 l L 5 13 33 INDUCTION UNITCONTROL SYSTEM BACKGROUND AND SUMMARY or THE INVENTION In theconstruction of air conditioning systems for high rise buildings, it iscommon to build the system so that the primary air is delivered withinparticular zones. For purposes of simplification, assume a 60 storybuilding approximately 600 ft. high. Normal practice would be to provideair conditioning systems for three zones, for example the to 180 ft.level; the 180 ft. to 400 ft. level; and the 400 ft. to 600 ft. level.Under this assumption then, three primary I air blowers would be locatedat the 100 ft., 300 ft., and 500 ft. levels.

One of the problems which has been encountered in the operation of suchsystems is that there exists a substantial pressure gradient between thefirst floor and the uppermost floor. Moreover, this pressure gradient isaffected further by temperature changes and wind direction and velocity.I

In the conventional induction unit system which, for example, is shownin U.S. Pat. No. 2,783,979, the principle by which the system operatesis essentially as follows:

Each individual room, or group of rooms, within the building is providedwith one or more induction units which comprise a heating (cooling) coiladapted to be supplied with a heated or chilled heat exchange medium, aplenum into which primary air is delivered, a means, such as a nozzle ora group of nozzles, into which the primary air is directed into a mixingchamber at high velocity, thereby creating a low pressure zonedownstream from the nozzles and, finally, an opening in the housing intowhich room air is drawn by means of the low pressure zone, and caused tocirculate over the coil and back into the room. The normal operation ofthese units is to provide cool primary air in the winter, whilesupplying a heated medium to the coil. In the summer, warm primary airis supplied to the units, while a chilled medium is circulated throughthe coil.

If it were not for the fact that the pressure gradient changes underdifferent conditions such as those mentioned earlier, each of theindividual induction units could be set for the particular conditionexisting at that point and left alone to operate satisfactorily.However, because of the pressure gradient changes, this causes imbalancein the units, and unless they are constantly being adjusted, there arechanges in the operation of the induction units which createinsufficient or too much heating or cooling at different times.

The present invention proposes to solve this problem by the use ofindividual dampers automatically controlled so as to maintain apredetermined pressure differential across the nozzle plate, that is,from the plenum to the mixing chamber. This damper is ofa low cost,simplified design, and can be added to existing units with very littleexpense. The damper is in the form of a screen which is adapted tocontrol the flow of air into the plenum chamber by opening and closing aport on the inlet side of the plenum. The position of the screen may becontrolled by a simple pneumatic actuator, such as a bellows, operatedthrough a system of levers or mechanical linkages.

It is, therefore, a principal object of this invention to provide animproved induction unit control system for a multiroom air conditioningsystem.

Another object of the invention is to provide an improved damperassembly for use with an induction unit system.

Additional objects and advantages will become apparent from reading thefollowing description taken in conjunction with the drawings.

DESCRIPTION OF THE DRAWINGS FIG. I is a transverse cross-sectional viewof an induction unit having a primary air supply control constructed inaccordance with the principles of this invention;

FIG. 2 is a longitudinal sectional view of the induction unit ofFIG. 2;and

FIG. 3 is a detailed, cross-sectional view of the damper control system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, theair conditioning unit 1 is of the induction type usually placed beneaththe window of a room being treated. The unit comprises a casing 2 havingan inlet opening 3 and an outlet opening 4, each opening consisting of aseries of louvered openings through which a stream of secondary air isinduced into the unit and a mixture of primary and secondary air isdischarged from the unit. A heat exchange member 10 is supported onbrackets 11 and 12 on the casing 2.

The air conditioning unit also has a plenum 5 located at the bottomportion of the casing 2 and consists of an elongated chamber extendingthe length of the casing and having an air inlet 6 through which primaryair passes into the plenum. This primary air is supplied under pressurefrom a blower (not shown) located at a central station. The air isdirected into plenum 5 and is discharged therefrom through the nozzles 8into the mixing chamber 14.

The nozzles 8 may be of severalknown types, but in the embodimentillustrated, they comprise a plurality of openings in a plate 13extending the length of the casing 2 and through which air is passed tothe mixing chamber 14 above the plenum. When air passes through thenozzles, the Bernoulli effect draws secondary air from the room throughthe opening 3 and into the chamber 13 where the primary and secondaryair streams are then mixed.

Located above the plenum 5 and the nozzle plate 13 is the heat exchangemember 10 comprising a plurality of parallel, extended fins l5 and aplurality of tubes 16 connected into a single circuit through which aheat exchange medium is passed. The fins 15 are attached to these tubesand act as an extended surface thereof. The aforementioned heat exchangemedium originates from a central station of the air conditioning systemand may consist of either hot or cold water.

As the primary air is discharged from the nozzles 8, secondary air isinduced through the opening 3 from the room and is mixed with theprimary air and this air mixture flows through the heat exchange member10 and is thereby placed into heat exchange relation with the mediumpassing through the tubes 16. The treated air mixture is then dischargedthrough the outlet 4 into the room.

Referring to FIG. 1, it will be noted that the primary air, passing intoinlet 6 and through plenum 5, is caused by the nozzles 8 to be expelledat high velocity into mixing chamber 14 thereby creating a low pressurezone downstream from the nozzles. By reason of the created low pressurezone, the secondary room air is drawn through opening 3 into the mixingchamber, the primary and secondary air mixture circulating over the heatexchange coils and back into the room. In normal operation, these unitsprovide cool primary air in the winter, while supplying a heated mediumto the coil 16. In summer, warm primary air is supplied to the units anda chilled medium is circulated through the coil 16.

Air conditioning systems of the induction unit type described areconventionally employed in tall buildings with the primary air deliveredby individual air conditioning systems provided in zones verticallyspaced in the building. In this arrangement, a substantial pressuregradient exists between the first floor and the uppermost floor of eachzone. Furthermore, this pressure gradient is also affected bytemperature changes and wind direction and velocity. More particularly,an analysis of stack effect pressure changes within high rise buildingsshows that the difference between ambient or secondary air pressures ata point more than 8 or 10 stories above or below the primary air sourcefan room and the ambient pressure at the fan room causes problems byupsetting the ratio of primary to secondary air pressures within theinduction units. Since the ambient secondary air pressure varies in onedirection as the heating season becomes more severe, and in the oppositedirection as the cooling season becomes more demanding, no singlesetting of a manually adjusted damper in each induction unit issatisfactory for producing the desired primary air pressure tocompensate for the changes in the ambient air pressure gradients.

The present invention provides a solution to this problem by employingmeans for automatically controlling the primary air pressure in theindividual air conditioning induction units relative to the surroundingambient air and more particularly by employing a control device for adamper which is automatically operative to vary the position of thedamper to regulate the flow of air into the plenum chamber by openingand closing a port on the primary air inlet side of the plenum.

The improved induction unit control system comprises a damper 17 anddamper control device 18. The damper 17 is positioned at the bottom ofthe plenum 5 and includes a screen or curtain 16 provided by anelongated, flexible, imperforate sheet of suitable material wound abouta shaft or roller 20 and having one end portion fastened by mechanicalholding means, such as rivets 21, to a plate 22 extending between andconnected, as by welding, to the front and rear walls 23 and 24 and sidewalls 25 and 26 of the casing 2. As seen in FIG. 3, the plate 22 islocated in the plenum 5 and forms a partition between the primary inletair duct 27 and the nozzle plate 13.

The roller 20 has end trunnions 28 received in slots 29 in the sidewalls 25 and 26 of the casing 2 for supporting the roller and formovement of the roller between the front and rear walls 23 and 24 ofeasing 2 to wind and unwind the curtain on the roller to provide foradjustable partial covering ofa generally frustoconical opening or port30 in the plate 22 to thereby vary the area of the opening andconsequent control of flow of primary air from the duct 27 into theplenum chamber 5.

Movement of the roller 20 is controlled by torsion springs 31 at bothends of the roller which have one end connected to the roller and itsother end connected to the trunnions 28. The springs 31 are operative tobias the roller in a direction tending to wind the curtain 16 on theroller and to the open position shown in the drawing.

The control device 18 is provided to automatically regulate movementofthe roller to vary the position of the damper curtain and thereby theopening and closing of the port 30 by the curtain to control the flow ofprimary air into the plenum. More particularly, the control device 18comprises an axially extensible bellows 33 having its lower end wallsealed around and fixed to a circular disk 34, the upper circular end ofthe bellows being sealingly connected t the bottom of the nozzle plate13 to prevent primary air in plenum chamber 5 entering the bellows. Theplate 13 is provided with an opening receiving an air tube 35 connectingthe bellows chamber with chamber 14 to permit secondary air in chamber14 to flow to and from the bellows. A coiled compression spring 9 islocated in the bellows with its lower end seated against the disk 34 andits upper end engaging a washer-like head of a bolt 7, the boltextending upwardly through the plate 13 and being threaded into plate 13and rotatable to vary the compression of spring 9. A flexible wire orcable 36 is secured to the center of the disk 34, extends downwardlythrough an opening in plate 22, and engages a pulley 37 rotatablysupported on a bracket 38 secured to the casing 2 as shown in FIG. 1.The wire 36 extends horizontally from the pulley 37 and is connected toa rigid U-shaped frame 39 intermediate the ends thereof, the framehaving the loop ends of its legs 40 surrounding the trunnions 28 of theroller 20 for moving the roller toward the damper-closing position ofthecurtain 19.

As previously explained, the rise and fall of the ambient room airpressures between the first floor and uppermost floor in high risebuildings during winter and summer, coupled with other pressure gradientchanges attributable to temperature changes and wind direction andvelocity, can create an imbalance in the induction units causingundesirable operational changes in the units and thus providinginsufficient or too much heating or cooling at different times. Itshould be noted that the difference in temperature between the air inthe duct and the ambient within the building also creates a disturbingpressure gradient which requires the damper control of the presentinvention.

To solve this problem and referring to the operation of the dampercontrol device 18 in the preferred embodiment of the invention, thebellows 33 provides a pneumatically operated pressure regulatorresponsive to variations in ambient air pressure entering opening 3 inthe casing 2 and flowing into the chamber 14. The device is arranged toautomatically effect adjustment of the damper in a manner to compensatefor such variations to thereby maintain a constant pressure in thechamber 14 relative to the surrounding ambient air pressure. Moreparticularly and referring to the drawing, primary air is directed athigh velocity through duct 27 and port 30 of plate 22 and into theplenum chamber 5 and then through the nozzles 8 into the mixing chamber14. At the same time, a low pressure zone is created downstream of thenozzles in chamber 14 causing secondary room or ambient air to be drawninto the chamber 14 and to mix with the primary air, the air mixturecirculating over the coils l6 and exiting through louvered openings 4into the room.

Assuming changes occur in the ambient or room air pressure, the bellows33 senses the differential between the primary air (plenum) pressure andambient pressure and adjusts the damper curtain 22 to regulate the flowof theprimary air to maintain a constant differential between theprimary air pressure and the ambient pressure, namely, to provide an airpressure in plenum 5 which is constant relative to ambient air pressureat opening 3 of the casing 2. As the tube 35 vents the bellows to theambient pressure at opening 3, a fall in ambient pressure at opening 3will cause the bellows to contract and pull cable 36 and frame 39 tomove the roller to unroll the curtain 22 over the port 30 and therebyreduce the primary air flow through the port and into the plenum 5; and,conversely, a rise in the ambient pressure at opening 3 will cause thebellows to expand so that the torsion springs 31 will provide arestoring force to the roller to re-roll the curtain and therebywithdraw the curtain over the port 39 to increase the flow of airthrough the port into the plenum 5. Accordingly, plenum 5 always retainsessentially the same nozzle pressure in any induction unit regardless ofthe location of the unit in the building and irrespective of the levelof the unit in relation to the primary air source. The result is moreuniform control of heating and cooling. Furthermore, since the pressuregradient within the supply ducts serving the different levels, such asthe O to ft. level, the 180 ft. to 400 ft. level, etc., varies withineach duct system, the supply pressure at 6 in the various units in thebuilding will be different. This would result in a different flow anddifferent pressure within the supply plenum were it not for the actionof the bellows and damper which corrects for these changes in supplypressure.

For the purpose of varying the desired pressure in plenum 5, thepressure of spring 9 in bellows 33 may be changed by rotating the bolt 7to move the bolt down or up to increase or decrease the compressiveforce of the spring acting on the disk 34.

While the invention has been described in connection with a certainspecific embodiment thereof, it is to be understood that this is by wayof illustration and not by way of limitation; and the scope of theappended claims should be construed as broadly as the prior art willpermit.

What is claimed is:

1. In an air conditioning unit, the combination of a casing (2); apartition (13) in said casing and providing a plenum chamber (5) and amixing chamber (14); means defining a first inlet (6) in said casing forprimary air under constant pressure and communicating with said plenumchamber; means defining a second inlet (3) in said casing for ambientsecondary air from the area being conditioned and communicating withsaid mixing chamber; means defining an outlet (4) in said casing andcommunicating with said mixing chamber; nozzle means (8) provided bysaid partition and connecting said chambers whereby the discharge ofprimary I air through said nozzle means and into said mixing chamberinduces a stream of secondary air through said second inlet to mix withthe primary air discharged from the plenum chamber, the mixture beingdischarged through said outlet; a heat exchanger disposed in said mixingchamber; a plate member (22) supported in said casing and providing anair port communicating said first inlet with said plenum chamber; adamper assembly (17) including a curtain (16), means (20, 21, 28, 29)for mounting said curtain on said plate member at one side of said airport and for movement of said curtain over said air port to thereby varythe flow of primary air to said nozzle means; spring means (31) biasingsaid curtain to open said air port; and means (18)automatically-controlling movement of said curtain over said air portincluding an expansible and contractable bellows (33) in said plenumchamber having one end fixed to said partition and a movable wall 34coupled to said curtain at the other side of said air port for movingsaid curtain; and a tube extending through said partition andcommunicating with the interior of said bellows and having its inletlocated in the ambient secondary air entering said second inlet (3) tocontrol movement of said movable wall in response to varying pressure ofthe ambient secondary air.

2. An air conditioning unit according to claim 1 in which said curtainmounting means (20, 21, 28, 29) includes a roller (20) having its ends(28) supported on spaced walls (25, 26) of said casing (2), and formovement toward said bellows (33), said curtain being wrapped aroundsaid roller and having one end connected to said plate member (22), saidroller ends (28) being also connected to said movable wall of saidbellows (33) whereby movement of said movable wall (34) is operative tomove said roller toward said bellows to unwrap said curtain from saidroller to open and close said air port (30) to change the flow ofprimary air into said plenum chamber (5).

3. An air conditioning unit according to claim 2 in which said springmeans are tension springs (31) connected to said roller ends (28) and tosaid casing (2).

4. An air conditioning unit according to claim 2 in which a U-shapedframe (39) is connected to said movable wall with its spaced armsconnected to said roller ends (28).

5. An air conditioning unit according to claim 4 in which a pulley (37)is supported on said casing (2), below said bellows (33), and a flexiblecable (36) engages said pulley and has its opposite ends connected tosaid frame (39) and said movable wall.

6. An air conditioning unit according to claim 1 in which a spring (9)is positioned in said bellows (33) to expand said bellows in oppositionto the contractive effort exerted on said bellows by air pressurechanges in said bellows.

7. An air conditioning unit'according toclaim 6 in which said spring (9)is a compression coil spring having one end engaging said movable wallsaid bellows (33), and an adjusting member (7) of one end engaging theother end of said spring, the other end of said adjusting member havingthreaded engagement with said partition (13) and being rotatable to movesaid adjusting member to vary the compression of said spring.

8. in an air conditioning unit, the combination of a casing (2); apartition (13) in said casing and providing a plenum chamber (5) and amixing chamber (14); means defining a first inlet (6) in said casing forprimary air and communicating with said plenum chamber; means defining asecond inlet (3) in said casing for ambient secondary air from the areabeing conditioned and communicating with said mixing chamber; meansdefining an outlet (4) in said casing and communicatingiwith said mixingchamber; nozzle means (8) provided by said partition and connecting saidchambers whereby the discharge of primary air through said nozzle meansand into said mixing chamber induces a stream of secondary air throughsaid second inlet to mix with the primary air discharged from the plenumchamber, the mixture being discharged through said outlet; a heatexchanger (10) disposed in said mixing chamber; a damper (17) positionedin said casing and operative to vary the flow of rirnary air into saidplenum chamber, said damper (17) tnc udmg a curtain (16) movabletransversely of the primary air flow and spring means (31) biasing saidcurtain (16) in a direction transversely of the primary air flow; andmeans (18) for automatically controlling operation of said damper inresponse to difference in the pressures in the primary air existing insaid plenum chamber and ambient secondary air entering said second inlet(3), said automatic controlling means operative to move said curtain ina direction opposite to that of the biasing force exerted by said springmeans (31 9. An air conditioning unit according to claim 8 wherein saidautomatic control means (18) is a pneumatically operated device.

10. An air conditioning unit according to claim 9 in which said primaryair is under substantially constant pressure, said automatic controllingmeans (18) for said damper (17) being responsive to pressures of theambient secondary air entering said second inlet (3).

UNITED STATES PATENT OFFICE CERTIFICATE OF CORREGTION Patent No. 3 6503320 Dated March 21, 197;

Inventor(s) Ahgjn B, Newton It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 6, line 6, after wall" insert 34) of line 7, cancel "of" firstoccurrence, and insert having Signed and sealed this 31st day of October1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-1050 (IO-69) USCOMM-DC 60376-P6D Q U.S, GOVERNMENTPRINTING OFFICE 1 I959 -3$6-33d,

1. In an air conditioning unit, the combination of a casing (2); apartition (13) in said casing and providing a plenum chamber (5) and amixing chamber (14); means defining a first inlet (6) in said casing forprimary air under constant pressure and communicating with said plenumchamber; means defining a second inlet (3) in said casing for ambientsecondary air from the area being conditioned and communicating withsaid mixing chamber; means defining an outlet (4) in said casing andcommunicating with said mixing chamber; nozzle means (8) provided bysaid partition and connecting said chambers whereby the discharge ofprimary air through said nozzle means and into said mixing chamberinduces a stream of secondary air through said second inlet to mix withthe primary air discharged from the plenum chamber, the mixture beingdischarged through said outlet; a heat exchanger (10) disposed in saidmixing chamber; a plate member (22) supported in said casing andproviding an air port (30) communicating said first inlet with saidplenum chamber; a damper assembly (17) including a curtain (16), means(20, 21, 28, 29) for mounting said curtain on said plate member at oneside of said air port and for movement of said curtain over said airport to thereby vary the flow of primary air to said nozzle means;spring means (31) biasing said curtain to open said air port; and means(18) automatically-controlling movement of said curtain over said airport including an expansible and contractable bellows (33) in saidplenum chamber having one end fixed to said partition and a movable wall34 coupled to said curtain at the other side of said air port for movingsaid curtain; and a tube (35) extending through said partition andcommunicating with the interior of said bellows and having its inletlocated in the ambient secondary air entering said second inlet (3) tocontrol movement of said movable wall in response to varying pressure ofthe ambient secondary air.
 2. An air conditioning unit according toclaim 1 in which said curtain mounting means (20, 21, 28, 29) includes aroller (20) having its ends (28) supported on spaced walls (25, 26) ofsaid casing (2), and for movement toward said bellows (33), said curtainbeing wrapped around said roller and having one end connected to saidplate member (22), said roller ends (28) being also connected to saidmovable wall of said bellows (33) whereby movement of said movable wall(34) is operative to move said roller toward said bellows to unwrap saidcurtain from said roller to open and close said air port (30) to changethe flow of primary air into said plenum chamber (5).
 3. An airconditioning unit according to claim 2 in which said spring means aretension springs (31) connected to said roller ends (28) and to saidcasing (2).
 4. An air conditioning unit according to claim 2 in which aU-shaped frame (39) is connected to said movable wall with its spacedarms (40) connected to said roller ends (28).
 5. An air conditioningunit according to claim 4 in which a pulley (37) is supporteD on saidcasing (2), below said bellows (33), and a flexible cable (36) engagessaid pulley and has its opposite ends connected to said frame (39) andsaid movable wall.
 6. An air conditioning unit according to claim 1 inwhich a spring (9) is positioned in said bellows (33) to expand saidbellows in opposition to the contractive effort exerted on said bellowsby air pressure changes in said bellows.
 7. An air conditioning unitaccording to claim 6 in which said spring (9) is a compression coilspring having one end engaging said movable wall said bellows (33), andan adjusting member (7) of one end engaging the other end of saidspring, the other end of said adjusting member having threadedengagement with said partition (13) and being rotatable to move saidadjusting member to vary the compression of said spring.
 8. In an airconditioning unit, the combination of a casing (2); a partition (13) insaid casing and providing a plenum chamber (5) and a mixing chamber(14); means defining a first inlet (6) in said casing for primary airand communicating with said plenum chamber; means defining a secondinlet (3) in said casing for ambient secondary air from the area beingconditioned and communicating with said mixing chamber; means definingan outlet (4) in said casing and communicating with said mixing chamber;nozzle means (8) provided by said partition and connecting said chamberswhereby the discharge of primary air through said nozzle means and intosaid mixing chamber induces a stream of secondary air through saidsecond inlet to mix with the primary air discharged from the plenumchamber, the mixture being discharged through said outlet; a heatexchanger (10) disposed in said mixing chamber; a damper (17) positionedin said casing and operative to vary the flow of primary air into saidplenum chamber, said damper (17) including a curtain (16) movabletransversely of the primary air flow and spring means (31) biasing saidcurtain (16) in a direction transversely of the primary air flow; andmeans (18) for automatically controlling operation of said damper inresponse to difference in the pressures in the primary air existing insaid plenum chamber and ambient secondary air entering said second inlet(3), said automatic controlling means operative to move said curtain ina direction opposite to that of the biasing force exerted by said springmeans (31).
 9. An air conditioning unit according to claim 8 whereinsaid automatic control means (18) is a pneumatically operated device.10. An air conditioning unit according to claim 9 in which said primaryair is under substantially constant pressure, said automatic controllingmeans (18) for said damper (17) being responsive to pressures of theambient secondary air entering said second inlet (3).